CN106340370B

CN106340370B - Coil component and method for manufacturing same

Info

Publication number: CN106340370B
Application number: CN201610537808.2A
Authority: CN
Inventors: 御子神祐; 高木信雄; 大井康裕; 芦泽瞬; 土田节
Original assignee: TDK Corp
Current assignee: TDK Corp
Priority date: 2015-07-10
Filing date: 2016-07-08
Publication date: 2021-08-13
Anticipated expiration: 2036-07-08
Also published as: CN106340370A; US20170011844A1; US10186376B2

Abstract

A coil component is provided to improve the dielectric strength of the coil component. A coil component of the present invention includes: a plurality of coated wires (S1-S4) constituting a first winding layer wound around a winding core part (11a) and a second winding layer wound around the first winding layer, and a resin coating layer (20) covering the coated wires (S1-S4). The maximum space (W1) of the covered conductor (S1, S4) constituting the first winding layer is larger than the wire diameter of the covered conductor

And (3) narrow. The coil component of the invention restrains the movement of the coated conducting wire, and the maximum space (W1) of the first winding layer is larger than the wire diameter of the coated conducting wire

Therefore, a high dielectric breakdown voltage can be ensured.

Description

Coil component and method for manufacturing same

Technical Field

The present invention relates to a coil component and a method for manufacturing the same, and more particularly to a coil component using a drum core and a method for manufacturing the same.

Background

In recent years, electronic components used in information terminals such as smartphones are strongly required to be downsized and thinned. Therefore, a surface-mount type coil component using a drum core is widely used without using a ring core for a coil component such as a pulse transformer. For example, patent document 1 discloses a surface-mount type step-up transformer using a drum core.

Further miniaturization and thinning are also required for a coil component using a drum core. Therefore, the size of the winding core portion is reduced every year, and a coated wire having a smaller wire diameter is used to secure a required inductance.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2012-119568

Problems to be solved by the invention

However, since the insulation withstand voltage of the covered wire having a small wire diameter is low, the insulation withstand voltage may be insufficient in a coil component such as a pulse transformer that needs to insulate a primary winding and a secondary winding. In particular, in the case of wiring by thermocompression bonding or laser bonding, heat applied at the time of wiring is transmitted through the core material covering the lead wire to deteriorate the covering film, and therefore, there is a problem that the insulation withstand voltage tends to be insufficient.

The present inventors have studied a method of using a coated wire coated with a low-melting-point resin film as a method of improving the dielectric strength of a coil component. When a coated wire coated with a resin film is used, the resin film is melted by the subsequent heat treatment, and the resin covers the defective portions such as scratches and cracks existing in the coated film. Therefore, it is expected to prevent the reduction of the dielectric breakdown voltage due to the defective portion.

However, according to the study of the present inventors, it has been found that if the thickness of the coated resin film is excessive, a strong stress is applied to the coated wires when the melted resin film is cooled and solidified, and the coated wires arranged in the row first move greatly.

The movement of the coated wire does not affect the basic performance of the coil component such as inductance. However, according to the study of the present inventors, it is found that when the movement of the covered wire is significant, the dielectric breakdown voltage is slightly lowered as compared with the case where it is not. This is considered to be mainly due to the fact that the distance between the clad wires is locally narrowed due to the movement of the clad wires, and thus, the electric field between the primary winding and the secondary winding becomes strong.

Disclosure of Invention

Accordingly, an object of the present invention is to provide a coil component using a coated wire coated with a resin film, which can obtain a higher dielectric strength, and a method for manufacturing the same.

Means for solving the problems

The present invention provides a coil component, comprising: a drum core including first and second flange portions and a core portion located between the first and second flange portions; a plurality of coated wires constituting a first winding layer wound around the winding core and a second winding layer wound around the first winding layer; and a resin coating layer covering the coated conductor, wherein a maximum space of the coated conductor constituting the first winding layer is narrower than a wire diameter of the coated conductor.

According to the studies of the present inventors, it has been found that, in a coil component using a coated wire coated with a resin film, a space generated in the first winding layer becomes equal to or larger than the wire diameter of the coated wire, and is a signal with a reduced withstand voltage. In contrast, the coil component of the present invention suppresses the movement of the covered wire, and the maximum space of the first winding layer is narrower than the wire diameter of the covered wire, so that a high insulation withstand voltage can be secured.

In the present invention, it is preferable that the maximum space of the covered conductor constituting the second winding layer is narrower than the wire diameter of the covered conductor. Accordingly, the movement of the covered wire is further suppressed, and therefore, a higher insulation withstand voltage can be ensured.

In the present invention, it is preferable that each of the first and second flange portions has a plurality of wire connecting portions, and both end portions of the plurality of covered wires are connected to the corresponding wire connecting portions. In this case, the plurality of covered wires preferably include a primary winding and a secondary winding that are insulated from each other. This is because such a coil component is often required to have a higher dielectric breakdown voltage.

In the present invention, it is preferable that the wire connecting portion is not covered with the resin coating layer. This prevents poor connection due to the resin coating layer, and prevents a decrease in wettability of the solder.

The present invention provides a method for manufacturing a coil component, comprising: a step of winding a plurality of coated wires, each having a coating film covering a core material and a resin film covering the coating film, around a winding core of a drum core, thereby forming a first winding layer wound around the winding core and a second winding layer wound around the first winding layer; connecting both end portions of the plurality of covered wires to wire connection portions provided on first and second flange portions of the drum core; and a step of forming a resin coating layer covering the plurality of coated wires by melting the resin film, wherein the maximum space of the coated wire constituting the first winding layer after melting is narrower than the wire diameter of the coated wire.

According to the present invention, since the resin coating layer is formed by melting the resin film, a flaw or the like of the coating film can be repaired, thereby improving the dielectric breakdown voltage. Further, since it is not necessary to apply a resin material or the like after winding the covered wire, the number of steps does not increase. In addition, since the movement of the coated wire accompanying the shrinkage of the resin coating layer is suppressed, a high insulation withstand voltage can be ensured.

In the present invention, the step of connecting is preferably performed by thermocompression bonding or laser bonding. This is because, when wiring is performed by thermocompression bonding or laser bonding, the dielectric breakdown voltage tends to be insufficient due to heat applied at the time of wiring.

In this case, it is preferable that the plurality of covered wires include a first covered wire constituting the first winding layer and a second covered wire constituting the second winding layer, and the step of connecting includes a step of connecting the first covered wire to the wire connecting portion and then connecting the second covered wire to the wire connecting portion. This is because the influence of heat is more significant when the wiring work is performed a plurality of times.

Preferably, the method for manufacturing a coil component according to the present invention further includes a step of bonding a plate-shaped core to the first and second flange portions, and the resin film is melted by heat applied in the bonding step. Accordingly, the bonding step of the plate-shaped core and the melting step of the resin film can be performed in the same step.

Effects of the invention

As described above, according to the present invention, it is possible to improve a coil component using a coated wire coated with a resin film and a method for manufacturing the same, and to obtain a coil component having a higher dielectric strength and a method for manufacturing the same.

Drawings

Fig. 1 is a schematic perspective view showing an external configuration of a coil component 10 according to a first embodiment of the present invention;

fig. 2 is an equivalent circuit of the coil component 10;

FIG. 3 is a cross-sectional view taken along line A-A' of FIG. 1;

fig. 4 is a schematic cross-sectional view showing a part of the first winding layer and the second winding layer in an enlarged manner;

fig. 5 is a schematic cross-sectional view showing a part of the first winding layer and the second winding layer in an enlarged manner;

FIG. 6 is a sectional view showing the structure of covered wires S1 to S4;

fig. 7(a) is a plan view showing a state in which covered wires S1, S4 constituting a first winding layer are wound, and fig. 7(b) is a plan view showing a state in which covered wires S2, S3 constituting a second winding layer are wound;

fig. 8 is a schematic plan view showing the structure of a coil component 13 according to a second embodiment of the present invention;

fig. 9 is a cross-sectional view showing an example of an xz cross-section of the winding core portion 11a of the drum core 11;

fig. 10 is a graph showing the measurement result of the maximum space W1;

FIG. 11 is a graph showing the results of the measurement of the withstand voltage;

fig. 12(a) is a photograph of a cross section of sample a, and fig. 12(B) is a photograph of a cross section of sample B.

Description of the symbols

10 coil component

11 drum core

11a core part

11b first flange part

11c second flange part

11bs upper surface of first flange portion

11cs upper surface of second flange portion

12 plate core

13 coil component

14 upper surface of the core

15 lower surface of the roll core

20 resin coating layer

31 core material

32 coating film

33 resin film

CT center tap

E1-E6, E3a, E3b, E4a and E4b wire connecting part

S1-S4 coated lead

S1 a-S4 a cover one end of the lead

S1 b-S4 b covers the other end of the lead

V-shaped cavity

Maximum space of W1 first winding layer

Maximum space of W2 second winding layer

Wire diameter

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 is a schematic perspective view showing an external configuration of a coil component 10 according to a first embodiment of the present invention.

The coil component 10 of the present embodiment is a surface-mount pulse transformer, and as shown in fig. 1, includes: the drum core 11, the plate-like core 12 bonded to the drum core 11, and the covered wires S1 to S4 wound around the core portion 11a of the drum core 11. However, the coil component of the present invention is not limited to the pulse transformer, and may be other transformer components such as a balun and a step-up transformer, or may be a filter component such as a common mode choke coil.

The drum core 11 and the slab core 12 are made of a magnetic material having a high magnetic permeability, for example, a sintered body of Ni-Zn ferrite or Mn-Zn ferrite. In addition, a magnetic material having a high magnetic permeability such as Mn — Zn ferrite has a low intrinsic resistance and conductivity, which is generally the case.

The drum core 11 includes a rod-shaped winding core portion 11a and first and

second flange portions

11b and 11c provided at both ends of the winding core portion 11a in the y direction, and has a structure in which these portions are integrated. Coil component 10 is a component surface-mounted on a substrate in actual use, and is mounted in a state where upper surfaces 11bs, 11cs of

flanges

11b, 11c in the z direction face the substrate. Plate-shaped cores 12 are fixed to the lower surfaces of

flange portions

11b and 11c on the opposite sides of upper surfaces 11bs and 11cs by an adhesive. With this structure, a closed magnetic circuit is formed by the drum core 11 and the plate core 12.

On the upper surface 11bs of the

first flange

11b, 3 wire connecting portions E1 to E3 are provided as terminal electrodes. Further, on the upper surface 11cs of the

second flange portion

11c, 3 wire connecting portions E4 to E6 are provided as terminal electrodes. The wire connecting portions E1 to E6 are formed of L-shaped terminal fittings attached to the

corresponding flange portions

11b and 11 c. However, it is not essential to use terminal metal parts, and the wire connecting portions E1 to E6 may be formed of conductor films sintered on the surfaces of the corresponding

flanges

11b and 11 c. The wire connection portions E1 to E3 are arranged in this order from one end side in the x direction shown in fig. 1. Similarly, the wire connection portions E4 to E6 are also arranged in this order from one end side in the x direction. The ends of the covered leads S1 to S4 are connected to the wire connecting portions E1 to E6 by thermocompression bonding or laser bonding.

As shown in fig. 1, the interval between the wire connecting portion E2 and the wire connecting portion E3 is designed to be larger than the interval between the wire connecting portion E1 and the wire connecting portion E2. Also, the interval of the wire connecting portion E4 and the wire connecting portion E5 is designed to be larger than the interval of the wire connecting portion E5 and the wire connecting portion E6. This is to increase the withstand voltage between the primary winding formed of the covered wires S1, S2 and the secondary winding formed of the covered wires S3, S4.

The covered leads S1 to S4 have a structure in which a core material made of a good conductor is covered with an insulating cover film, and are wound around the winding core 11a in a two-layer structure. As will be described in detail later, the covered conductive wires S1 and S4 are wound in pairs around the winding core 11a to form a first winding layer, and the covered conductive wires S2 and S3 are wound in pairs around the first winding layer to form a second winding layer. The numbers of turns of the covered wires S1 to S4 are the same.

The winding directions of covered wires S1 to S4 are different between the first winding layer and the second winding layer. That is, when the winding direction from the first flange 11b toward the second flange 11c is viewed from the flange 11b side, the winding direction of the covered conductive wires S1 and S4 is counterclockwise, and the winding direction of the covered conductive wires S2 and S3 is clockwise, and opposite to each other.

One end S1a and the other end S1b of the covered wire S1 are connected to the wire connecting portions E1 and E4, respectively, and one end S4a and the other end S4b of the covered wire S4 are connected to the wire connecting portions E3 and E6, respectively. One end S2a and the other end S2b of the covered wire S2 are connected to the wire connecting portions E4 and E2, respectively, and one end S3a and the other end S3b of the covered wire S3 are connected to the wire connecting portions E5 and E3, respectively.

Fig. 2 is an equivalent circuit of the coil component 10 of the present embodiment.

As shown IN fig. 2, the wire connection portions E1, E2 serve as a positive electrode-side terminal IN + and a negative electrode-side terminal IN-of the balanced input, respectively. The wire connection portions E5 and E6 serve as a positive electrode-side terminal OUT + and a negative electrode-side terminal OUT-for balanced output, respectively. The connection portions E3 and E4 serve as intermediate taps CT on the input side and the output side, respectively. The covered wires S1, S2 constitute the primary winding of the pulse transformer, and the covered wires S3, S4 constitute the secondary winding of the pulse transformer.

Fig. 3 is a schematic sectional view taken along line a-a' shown in fig. 1.

As shown in fig. 3, the covered wires S1, S4 constituting the first winding layer are wound around the winding core 11a of the drum core 11, and the covered wires S2, S3 constituting the second winding layer are wound around the first winding layer. That is, the covered wires S1 to S4 wound around the winding core 11a have a double-layer structure. At least the surfaces of the covered wires S1 and S4 constituting the first winding layer are covered with the resin covering layer 20. The resin coating layer 20 is made of an insulating resin material having a low melting point, such as polyester. The resin coating layer 20 preferably covers the coated leads S2, S3 constituting the second wound layer, but in the present embodiment, the upper surfaces of the coated leads S2, S3 constituting the second wound layer may not be completely covered due to a manufacturing method described later.

Fig. 4 is a schematic cross-sectional view showing a part of the first winding layer and the second winding layer in an enlarged manner.

As shown in fig. 4, the covered conductive wires S1 to S4 have a structure in which the core material 31 is covered with the cover film 32. The resin coating layer 20 is provided so as to cover the coating films 32 that coat the lead wires S1 to S4. The covered wires S1 and S4 constituting the first winding layer are almost not exposed from the covering film 32, and substantially the entire surface is covered with the resin covering layer 20. It is also preferable that substantially the entire surface of covered wires S2 and S3 constituting the second winding layer be covered with resin covering layer 20.

In this way, in the coil component 10 of the present embodiment, since the covered lead wires S1 to S4 are covered with the resin covering layer 20, defective portions such as scratches and cracks existing in the covering film 32 are buried in the resin covering layer 20. Thus, it is possible to prevent a decrease in the dielectric breakdown voltage due to the defective portion and to ensure a high dielectric breakdown voltage.

Further, the resin coating layer 20 is preferably present only on the core portion 11a of the drum core 11, and the resin coating layer 20 is preferably absent on the

flange portions

11b and 11 c. That is, it is preferable that the resin coating layer 20 is not interposed between the

flange portions

11b and 11c and the plate core 12, and the wire connecting portions E1 to E6 are not covered with the resin coating layer 20.

As shown in fig. 4, the covered wires S1 and S4 are alternately arranged in the first winding layer, and the covered wires S2 and S3 are alternately arranged in the second winding layer. However, when the resin coating layer 20 melted by a thermal load during manufacture and mounting is cooled and solidified, stress acts on the coated conductive wires S1 to S4, and thus, as shown in fig. 5, a part of the entire row of the coated conductive wires S1 to S4 may move. As a result, unevenness occurs in the space between the adjacent covered wires S1 and S4 and the space between the adjacent covered wires S2 and S3.

However, in coil component 10 of the present embodiment, movement of covered wires S1 to S4 is suppressed, and thus maximum space W1 of covered wires S1 and S4 constituting the first winding layer is lower than the wire diameters of covered wires S1 to S4

In other words, no wire path is present in the first winding layer

The above space. It is preferable that the maximum space W2 of the covered wires S2 and S3 constituting the second winding layer is also suppressed to be smaller than the wire diameter

In addition, the maximum space W1 of the covered wires S1, S4 is preferably lower than the maximum space W2 of the covered wires S2, S3.

In the example shown in fig. 5, a large space W2 exists between the adjacent covered wires S2, S3, and as a result, a void V is formed therebetween. Such a hollow V may reach the first winding layer, and in this case, too, it is necessary that the maximum space W1 in the first winding layer be lower than the wire diameter of the covered conductor

It is necessary to set the maximum space W1 in the first winding layer to be lower than the wire diameter

The reason for (a) is as follows.

As will be described later, the resin coating layer 20 is derived from a resin film (fusion-bonded layer) that is initially applied to the surface of the coated lead wires S1 to S4, and the amount thereof can be adjusted according to the thickness of the resin film. However, when the thickness of the resin film is excessive, the molten resin coating layer 20 is cooled and solidified, and the coated conductive wires S1 to S4 arranged in the row first move greatly due to the shrinkage stress of the resin coating layer 20, and are deviated. As a result, the adjacent covered wires S1 and S4 or the adjacent covered wires S2 and S3 are locally tightly joined, and the withstand voltage is lowered. In addition, the excessive resin coating layer 20 increases the electric field between the coated wires, which leads to a decrease in withstand voltage.

This reduction in withstand voltage expands the maximum space W1 of the covered wires S1 and S4 constituting the first winding layer to the wire diameter

The above is remarkable. I.e. will be the mostJust below the wire diameter

Is expanded to the wire diameter

In the above case, the breakdown voltage is reduced. Therefore, it is necessary to thin the coated resin film to such an extent that such a phenomenon does not occur.

Next, a method for manufacturing the coil component 10 of the present embodiment will be described.

First, as shown in fig. 6, the covered wires S1 to S4 having a 3-layer structure including the core 31, the cover film 32, and the resin film 33 are prepared. The core member 31 is made of a good conductor such as copper (Cu), and the surface thereof is covered with a coating film 32. The cover film 32 is made of an insulating material such as imide-modified polyurethane, and its surface is covered with a thin resin film 33. The resin film 33 is made of an insulating resin material such as polyester, and a material having a sufficiently lower melting point than the cover film 32 can be selected. For example, imide-modified polyurethanes have a melting point of about 260 ℃ and polyesters have a melting point of about 70 ℃. The film thickness of the resin film 33 is set sufficiently thin within a range capable of repairing a defective portion of the cover film 32.

Next, as shown in fig. 7(a), the covered wires S1 and S4 are wound around the winding core 11a in a double-wound manner, and both ends thereof are connected to the corresponding wire connecting portions E1, E3, E4, and E6, respectively, thereby forming a first winding layer. Specifically, the covered wires S1 and S4 are wound around the core portion 11a by connecting the one ends S1a and S4a of the covered wires S1 and S4 to the wire connecting portions E1 and E3 by thermocompression bonding or laser bonding, respectively, and then rotating the drum core 11 in one direction. After the rotation of the drum core 11 is stopped, the other ends S1b and S4b of the covered wires S1 and S4 are connected to the wire connecting portions E4 and E6, respectively, by thermocompression bonding or laser bonding. At this time, since heat generated by thermocompression bonding or laser bonding is transmitted through the core material 31, the portion of the covered wire S1 or S4 near the end portion of the covering film 32 may deteriorate, and defects such as scratches or cracks may occur. Further, a defect may be generated in the cover film 32 due to a mechanical stress generated during winding. In addition, when thermocompression bonding or laser bonding is performed, the resin film 33 present at the one ends S1a and S4a and the other ends S1b and S4b of the covered wires S1 and S4 is deteriorated by heat. In the present invention, the resin coating layer 20 is not formed of resin that is deteriorated by heat during wiring.

Although not particularly limited, the covered wires S1 and S4 after being wound are preferably aligned in a state of being tightly bonded to each other via the resin film 33. Accordingly, the winding density of the first winding layer is maximized, and thus, the number of turns can be maximized. However, after winding, all of the adjacent covered wires S1, S4 do not have to be tightly joined, and a part of the covered wires S1, S4 may be separated to some extent. In this case, the maximum space of the covered conductive wires S1, S4 after winding needs to be smaller than the wire diameter of the covered conductive wires

This is because the maximum space of the covered wires S1, S4 after winding is

In the above case, the covered wires S2 and S3 constituting the second winding layer cannot be formed accurately.

Next, as shown in fig. 7(b), the covered wires S2 and S3 are wound around the winding core 11a in two-wire form, and both ends thereof are connected to the corresponding wire connecting portions E2, E3, E4, and E5, respectively, thereby forming a second winding layer. Specifically, the other ends S2b and S3b of the covered wires S2 and S3 are connected to the wire connecting portions E2 and E3 by thermocompression bonding or laser bonding, and then the drum core 11 is rotated in the opposite direction, whereby the covered wires S2 and S3 are wound around the winding core portion 11 a. After the rotation of the drum core 11 is stopped, the one ends S2a and S3a of the covered wires S2 and S3 are connected to the wire connecting portions E4 and E5, respectively, by thermocompression bonding or laser bonding.

Here, in the case where the covered wires S1, S4 constituting the first winding layer are closely joined, or the maximum space after at least winding is lower than

In the case of (2), the second winding layer may be constitutedThe covered wires S2 and S3 are correctly wound on the first winding layer. In contrast, when the wire diameter exists between the adjacent covered wires S1 and S4 after winding

In the above space, the covered wire S2 or S3 falls into the space, and the second wound layer cannot be formed correctly. For this reason, the maximum space of the covered conductive wires S1, S4 after winding is lower than the wire diameter of the covered conductive wires

Is adjusted.

When both ends of the covered wires S2, S3 are connected to the wire connecting portions E2, E3, E4, E5, the resin film 33 present at one ends S2a, S3a and the other ends S2b, S3b of the covered wires S2, S3 is deteriorated by heat at the time of wire connection. Further, since heat generated by thermocompression bonding or laser bonding is transmitted through the core material 31, the portion of the covered wire S1 to S4 near the end of the covering film 32 deteriorates.

Further, the covered wires S1 and S4 are subjected to thermal damage twice in total, namely, thermal damage by thermocompression bonding or laser bonding when forming the first layer and thermal damage by thermocompression bonding or laser bonding when forming the second layer, and therefore deterioration is likely to occur in the covering film 32. That is, one of the covered wires S1 and S4 constituting the first winding layer is damaged more largely than the covered wires S2 and S3 constituting the second winding layer, and defects such as scratches and cracks are more likely to occur in the cover film 32.

When the winding operation of the covered wires S1 to S4 is thus completed, the plate-shaped core 12 is bonded to the drum core 11 thereafter. Specifically, after a small amount of adhesive is supplied to the

flange portions

11b and 11c of the drum core 11, the plate-like core 12 is placed on the

flange portions

11b and 11c of the drum core 11. By performing the heat treatment in this state, the adhesive is cured, and the plate-shaped core 12 is fixed to the drum core 11. The heat treatment at this time is performed at 150 ℃ for about 1 hour, for example.

By this heat treatment, the resin film 33 present on the surfaces of the covered wires S1 to S4 melts and infiltrates into the gaps between the covered wires S1 to S4. At this time, when a defective portion such as a flaw or a crack exists in the coating film 32, the defective portion is buried in the resin coating layer 20 made of the melted resin film 33. Since the resin coating layer 20 made of the melted resin film 33 is concentrated around the coated wires S1 and S4 constituting the first winding layer by capillary action, at least substantially the entire first winding layer is covered with the resin coating layer 20. In contrast, depending on the thickness of the resin film 33, the second wound layer may be partially uncovered by the resin coating layer 20 and the coating film 32 may be exposed. Further, the resin films 33 present in the wire connecting portions E1 to E6 are not melted by heat treatment because they are modified by heat during wire connection.

When the heat treatment is completed, the melted resin coating layer 20 is cooled and solidified. Due to the stress generated at this time, the entire row of covered wires S1 to S4 moves, and the first winding layer and the second winding layer both generate a space between the adjacent covered wires. However, in the present embodiment, since the film thickness of the resin film 33 applied to the covered wires S1 to S4 is sufficiently thin, the amount of the resin covering layer 20 does not become excessive, and as a result, at least the maximum space W1 in the first winding layer can be suppressed to be lower than the wire diameter

In other words, after winding, the maximum space W1 is below the wire diameter

The maximum space W1 of the first winding layer (3) does not expand to the wire diameter even after the resin film 33 is melted and solidified

Above, but kept below the wire diameter

It is preferable that the maximum space W2 of the second wound layer does not spread to the wire diameter

Above, but kept belowWire diameter

As described above, the maximum space W1 of the first winding layer is expanded to a wire diameter

The above phenomenon is a signal generated when the dielectric breakdown voltage of the primary side and the secondary side is lowered. In the present embodiment, the film thickness of the resin film 33 is set sufficiently thin so as not to generate such a signal.

Through the above steps, the coil component 10 of the present embodiment is completed.

In this way, in the present embodiment, the resin coating layer 20 is formed by using the coated lead wires S1 to S4 whose surfaces are covered with the resin film 33 and melting the resin film 33 by the subsequent heat treatment. Therefore, the surfaces of the covered wires S1 to S4 are automatically covered with the resin covering layer 20. In particular, the covered wires S1, S4 constituting the first winding layer are thermally damaged twice, and therefore, defective portions are likely to be generated on the cover film 32. However, according to the present embodiment, since the surfaces of the covered wires S1 and S4 constituting the first winding layer are automatically covered with the resin covering layer 20, the defective portion of the covering film 32 generated in the first winding layer can be reliably buried in the resin covering layer 20. Thus, even when a defective portion occurs in the cover film 32, a sufficient dielectric breakdown voltage can be secured.

Here, in order to improve the dielectric strength, a method of winding the covered wires S1 to S4 around the winding core 11a and then applying a resin material may be considered. However, when the viscosity of the resin material is high, the covered wires S1 to S4 cannot be sufficiently coated, and when the viscosity of the resin material is low, the resin material flows into the

flange portions

11b, 11c of the drum core 11 by capillary action. In particular, in a thin coil component having a small height difference between the winding core 11a and the

flanges

11b and 11c, the resin material cannot flow into the coil component due to capillary action.

When the resin material flows into the lower surfaces of the

flange portions

11b and 11c, a gap is formed between the resin material and the plate-shaped core 12, and the magnetic properties are degraded. When the resin material flows into upper surfaces 11bs and 11cs of

flanges

11b and 11c, portions of wire connecting portions E1 to E6 as terminal electrodes are covered with the resin material, and wettability of solder at the time of mounting is lowered.

In contrast, in the present embodiment, the resin coating layer 20 is formed by performing the winding operation using the covered conductive wires S1 to S4 having the resin film 33 provided in advance on the surface thereof without applying the resin material to the wound covered conductive wires S1 to S4, and then melting the resin film 33, so that the resin material is unlikely to flow into the

flange portions

11b and 11 c. Further, the covered wires S1, S4 of the first layer, in which defective portions are more likely to be generated, can be reliably covered with the resin covering layer 20.

As described above, in the coil component 10 of the present embodiment, since the covered conductive wires S1 and S4 are covered with the resin covering layer 20, a sufficient dielectric strength can be ensured even when a covered conductive wire having a small wire diameter is used. Further, since the resin coating layer 20 does not reach the

flange portions

11b and 11c, a decrease in magnetic characteristics and a decrease in wettability by solder can be prevented.

In the present embodiment, since the coated lead wires S1 to S4 having a thin film thickness of the resin film 33 are used, the amount of the resin coating layer 20 is not excessive. Thus, a signal of the drop resistance is not generated.

Fig. 8 is a schematic plan view showing the structure of a coil component 13 according to a second embodiment of the present invention, showing the structure on the bottom surface side.

As shown in fig. 8, the coil component 13 according to the second embodiment is characterized in that the number of terminal portions provided in each of the

flanges

11b and 11c is 4 instead of 3. Flange portion 11b is provided with 4 wire connecting portions E1, E2, E3a, and E3b, and flange portion 11c is provided with 4 wire connecting portions E4a, E4b, E5, and E6. The electrical connection of the other end S1b of the covered wire S1 and the one end S2a of the covered wire S2 and the electrical connection of the other end S3b of the covered wire S3 and the one end S4a of the covered wire S4 are made via a wiring pattern (pad) on the mounting substrate when the coil component 13 is mounted. The other structures are the same as those of the coil component 10 of the first embodiment, and therefore, the same elements are denoted by the same reference numerals, and redundant description is omitted.

In this way, in the coil component 13 of the present embodiment, the two wire connecting portions E3a and E3b are short-circuited on the mounting substrate, and the two wire connecting portions E4a and E4b are further short-circuited, whereby the same configuration as that of the coil component 10 of the first embodiment can be realized. Therefore, the same operational effects as those of the first embodiment can be exerted.

Fig. 9 is a cross-sectional view showing an example of an xz cross section of the winding core portion 11a of the drum core 11.

In the example shown in fig. 9, the upper surface 14 and the lower surface 15 of the winding core 11a are arc-shaped. When such a winding core 11a having an arc-shaped cross section is used, the melted resin film 33 is more likely to wet the corner of the winding core 11a than when the winding core 11a having a rectangular cross section is used, and therefore, the coated lead wires S1 and S4 located at the corner of the winding core 11a can be reliably covered with the resin coating layer 20. In addition, if the cross section of the winding core portion 11a is oval or circular, the corner portions disappear, and therefore the covered conductive wires S1 and S4 can be covered with the resin covering layer 20 more reliably.

While the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention, and these are also encompassed in the scope of the present invention.

For example, in the above embodiment, the covered wire wound around the winding core portion has a double-layer structure, but the coil component of the present invention is not limited to this. Therefore, the covered wire may have a 3-layer structure or more.

The method of winding the covered conductor is not particularly limited, and the first winding layer and the second winding layer may be wound in two-wire simultaneously as in the embodiment, or the covered conductor may be wound one by one.

Examples

A drum core 11 having a shape shown in fig. 1, and having a length in the x direction of 4.5mm, a width in the y direction of 3.2mm, and a height in the z direction of 2.9mm was prepared. Further, the covered wires S1 to S4 each having a cross section shown in fig. 6, a diameter of the core material 31 of 40 μm, a thickness of the covering film 32 of 10 μm, and a thickness of the resin film 33 of 1 μm or 3.5 μm were prepared, and wound around the drum core 11 by the method described with reference to fig. 7. However, the formation of the wire portions E1 to E6 is omitted, and both ends of the covered wires S1 to S4 are opened. The samples using the covered wires S1 to S4 having a film thickness of 1 μm of the resin film 33 were designated as "sample A", and the samples using the covered wires S1 to S4 having a film thickness of 3.5 μm of the resin film 33 were designated as "sample B".

Next, the resin film 33 is melted by applying a heat load, and then cooled to form the resin coating layer 20. The application of the heat load was performed by a first heat treatment simulating bonding of the slab core and a second heat treatment simulating reflow at the time of mounting. Further, the maximum space W1 of the first wound layer was determined for each sample. The measurement results are shown in fig. 10.

As shown in FIG. 10, in sample A in which the covered wires S1 to S4 having a film thickness of 1 μm and the resin film 33 were used, the maximum space W1 of the first winding layer was 20 μm to 56 μm. On the other hand, in sample B using the covered wires S1 to S4 in which the resin film 33 had a film thickness of 3.5 μm, the maximum space W1 of the first winding layer was 61 μm to 107 μm. That is, in sample A, even after the covered wires S1 to S4 are moved by the thermal load, the maximum space W1 of the first winding layer does not exceed the wire diameter

In contrast, in sample B, the maximum space W1 of the first winding layer becomes the wire diameter after the covered wires S1 to S4 move due to the thermal load

The above.

Next, samples A, B each short-circuited the end S1a of the covered wire S1 to the end S2b of the covered wire S2 and connected to one detection terminal (+) of the multimeter, and short-circuited the end S3b of the covered wire S3 to the end S4a of the covered wire S4 and connected to the other detection terminal (-) of the multimeter. In this state, an alternating voltage of 50Hz was applied between the pair of detection terminals for 60 seconds to examine the presence or absence of dielectric breakdown. When the initial value of the voltage was 1.5kV and no dielectric breakdown occurred, the voltage was increased every 0.1kV, and an AC voltage was applied again. Further, the voltage at which the dielectric breakdown occurs is plotted. The results are shown in FIG. 11.

As shown in fig. 11, the voltage at which dielectric breakdown occurs in sample a was 4.7kV to 5.0kV, while the voltage at which dielectric breakdown occurs in sample B was 4.0kV to 4.7 kV. That is, it was confirmed that a high dielectric strength was obtained in sample a.

Next, sample A, B was cut so that the yz plane of core portion 11a was exposed, and the cross section was observed by SEM. The cross section of sample a is shown in fig. 12(a), and the cross section of sample B is shown in fig. 12 (B).

As shown in fig. 12(a), in sample a, the movement of the covered wires S1 to S4 is small, and large voids V are not formed in the resin covering layer 20. On the other hand, as shown in fig. 12(B), in sample B, the movement of the covered wires S1 to S4 is large, and a large cavity V reaching the winding core portion 11a is formed in the resin covering layer 20. Due to the existence of the large cavity V, a wire diameter is generated in the covered wires S1 and S4 constituting the first winding layer

The above space.

Claims

1. A coil component characterized in that,

the disclosed device is provided with:

a roll core;

a plurality of wires having the same wire diameter, which are wound around the winding core; and

a resin coating layer covering the wire,

the plurality of conductive lines include a first conductive line, a second conductive line, a third conductive line and a fourth conductive line,

the first wire and the fourth wire are wound around the winding core in a first direction,

the second conductive wire and the third conductive wire are wound around the winding core in a second direction opposite to the first direction,

the first and fourth wires form a lowermost winding layer on the winding core,

the second and third wires form an uppermost winding layer on the lowermost winding layer,

a first maximum space between the wires of the lowermost winding layer is narrower than a second maximum space between the wires of the uppermost winding layer,

the first maximum space is narrower than a wire diameter of the wire,

the first maximum space is filled with the resin coating layer in such a manner that the second or third wire does not enter the first maximum space.

2. The coil component of claim 1,

the second maximum space is narrower than a wire diameter of the wire.

3. The coil component of claim 1,

further comprises a first flange portion and a second flange portion,

the winding core is located between the first flange portion and the second flange portion,

the first flange portion includes a plurality of first wire connecting portions,

the second flange portion is provided with a plurality of second wire connecting portions,

one end of each of the wires is connected to a corresponding one of the first wiring parts,

the other end of each of the wires is connected to a corresponding one of the second wiring portions.

4. The coil component of claim 1,

the resin coating layer comprises polyester.

5. The coil component of claim 1,

each of the leads includes a core material and a coating film covering the core material,

the melting point of the resin coating layer is lower than that of the coating film.